Logic riddles

Yes, this is possible. First, break open all three links of one of the pieces of chain. This costs 3×1 = 3 euros. Then join the remaining four pieces of chain with the three open links. Welding these links costs 3×3 = 9 euros. The total costs are 12 euros.

Is it correct seven and five is thirteen or seven and five are thirteen?

Answer

Seven and five ARE thirteen is the correct way. Except that seven and five is actually 12

Prove that 2 + 8 + 9 = 10

Answer

2 (Two) + 8 (Eight) + 9 (Nine) = TEN (10)

Im a word. I become longer when the third letter is removed.
What am i?

Answer

Lounger.

I can bring tears to your eyes; resurrect the dead, make you smile, and reverse time. I form in an instant but I last a lifetime.
What am I?

Answer

A memory.

The day after tomorrow is the third day after Wednesday.
Which day was the day before yesterday?

Answer

The third day after Wednesday is Saturday. If the day after tomorrow is Saturday, then today is Thursday. Therefore, the solution is: the day before yesterday was Tuesday.